In the method documentation there is written

\param[in] ent Entity ent is an input parameter representing an entity in the game world that triggers the method's action when its state changes

When the desired entity enters the trigger (activation), the parameter of OnChange will be the SCR_ScenarioFrameworkTriggerEntity instance itself. However, when the desired entity leaves the trigger (deactivation) the parameter is instead the desired entity. This seems to me like an inconsistency. I read the doc as if the behaviour on entity exit (deactivation) is the correct behaviour, and that this should also be the case for trigger activation.